Electronic control system



Dect. 1.9, 1961 A. A. MACDONALD 3,014,215

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. Angus A Mocdonolcl M ATTORNE United States `atent O i 3,014,215 ELECTRONIC CONTROL SYSTEM Angus A. Macdonald, Catonsville, Md., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania s Filed Nov. 19, 1945, Ser. No. 629,658 6 Claims. (Cl. 343--17.1)

My invention relates to radio control systems and in particular relates to such systems in which a work circuit or control device is to be actuated upon a moving vehicle or other object when the distance separatingV the latter from a reilecting body reaches a certain value. For example, my control system is adapted to detonate bombs when they have approached to within a predetermined distance of la target.

One of the novel features of my invention is that it employs circuits Vwhich are energized only when electric pulses of a predetermined duration are impressed upon them to control the position at which the work circuit, such as a bomb detonator, will be activated. One of the advantages of such a device is that its actuation is, over a large range of values, independent of variations in the intensity of the radio waves acting upon it and also that it is comparatively unaiected by substantial changes lin the electrical characteristics of electron tubes employed in the system. It thereby avoids certain defects characteristic of other arrangements for controlling detonating operations and the like by means of reflected electromagnetic waves.

' One object of my invention is accordingly to provide a system employing reilected wave pulses separated from each other by intervals long compared with the pulse duration for controlling work circuits by a system which is to a large degree independent of Variations in intensit of the transmitted or reflected pulses. v

Another object of my invention is to provide a system in which reflected wave pulses control a work circuit in response to energiz'ation thereof for the criticaly time period only. 'l

A further object of my invention is to provide a system employing intermittent radio pulses and their reflections from a target to actuate work circuits when a moving body has attained a predetermined distance from said target andpin which the actuation is controlled in response to the duration of the recurrent pulses.

Still another object of my invention is to provide a system in which the work circuit is controlled by the interfering acti-on of pulsed radio waves and in which the control of the work circuit `is responsive to a predetermined overlap in time between the transmitted and reilected waves incident upon the body.

A still further object of my invention is to provide a system in which `pulsed radio waves are reected from a tar-get and are received by a' control circuit on the body approaching the ltarget in which the distance from the target at which the control circuit is actuated is varied by varying the duration of the transmitted pulses.

`Other objects of my invention will become apparent upon reading Ithe ,following description taken in connec- .tion with the drawing, in which:

Patented Dec. 19, 1961 form of receiver for employing the system of my invenrtion.

Referring in detail to FIG. 1, a transmitter 1 of the type well known today in the radio art, which is adapted to send yout pulses of electromagnetic waves separated from each other by intervals large compared with the duration of the separate pulses, is positioned together with a radiating antenna 2 on a vehicle or other support from which it is desired to control the actuation of a work circuit positioned upon a vehicle or other device moving relative to said support. For example, where it is desired to control the point at which a bomb dropped by an airplane shall detonate, the transmitter 1 is located on the airplane. Since transmitters for generating intermittent pulses of high frequency waves are Well known in the art, it is not believed necessary to explain the circuits of the transmitter 1 in detail here.

On the moving body, e.g., the bomb, which it is desired to control, is positioned an antenna 3 adapted Vto received radiations from the transmitter 1 and also radiations reected from a third body such as a target. The antenna 3 controls a detector 4 which is arranged for automatic volume control by the circuits of an amplifier `in an automatic control device 5 fed from the output of the detector. Numerous types of detectors and ampliiiers embodying automatic volume control are known in the art, and -a particular type which now seems to me well suited for the purposes of this invention is shown in detail in FIG. 4. The output of the amplifier 5 is fed to a second amplier 6 which is provided with a circuit adapted to cause a marked change of current ow in its output in response to the transmission from the ampliier 5 of a current pulse of at least a predeterminedvduration. That is to say, current pulses from the output of amplifier 5 having a length substantially less than said predetermined value, leave unchanged the lcurrent magnitude in the output of the amplifier 6. The amplifier 6 may be referred to as embodying a pulse-width discriminator and such a discriminator is described in detail in FIG. 4.

The output of the amplifier 6 is supplied to a trigger tube 7 of which many types are well known in the art, one such being shown in FIG. 4 hereof, and causes energization of the output circuit of said trigger tube in response to the above mentioned substantial change in the output current of amplier 6. The output circuit of the trigger tube 7 :actuates 'any desired control device 8i for example, the detonator of a `ibornb on which the elements 3 through 8 are carried.

Referring to FIG. 2, the antenna 3 will, in general, receive a pulse of energy from transmitter 1 eachtime the latter emits a pulse; and will also, an instant later, receive a second pulse comprising the energy reected from the target when struck by the emitted pulse just mentioned. In this ligure, 11 represents the envelope of the pulse received directly from the transmitter 1 by the antenna 3 carried on the bomb or moving object, and 12 represents the envelope of the wave pulse received by that same antenna as a result of the reection from `the target of the pulse producing envelope 11. When the bomb orv moving object is 3000 feet distant vfrom the target, as will be seen from FIG. 2a, the pulse 12 does not occur in the antenna 3 until about 6 microseconds after the pulse 11.

vIn FIG. 2b, `the pulses 11 and 12 have the same signicance as the corresponding number ofpulses in FIG. 2a and represent conditions when the .bomb or moving object is 2000 feet distant from the target. 'It will be seen by comparing FIGS. 2a and 2b that thertime separating pulses 11 and 12 decreases in proportion yto the vdistance `separating the moving body and the target.

by 500 feet, the pulse 12 follows the pulse 11 without a break.

FIG. 2d represents the effect of the pulses 11 and 12 when the distance separating the body from the target has been reduced to 375 feet and shows that the two pulses overlap to produce a portion 13 having an amplitude equal to the sum of the amplitudes of the pulses 11 and 12.

FIGS. 2e and 2f represent, respectively, the pulses 11 and 12 when the distances separating the body from the target are 250 feet and 125 feet, and it is evident from them that the overl-ap 113 increases in width as the distance separating the body from the target decreases.

'-F-inally, FIG. 2g shows that when the distance separating the target from the body is reduced to zero, the pulses 11 and 12 overlap completely, coalescing to form by their overlap a single rectangular wa've form.

-In accordance with one feature of my invention, I cause the trigger tube 7 to be actuated only when the overlap 13 has a predetermined duration. By reason of the fact that the detector 4 and amplifier 5 are provided with automatic valume control the output of the amplifier 5 is unaiected over a wide range, by variations from time to time in the amplitude of the pulses 1.1 and 12; however, in accordance with the well known properties of automatic volume control circuits, the output current of the ampliiier 5 responds to the comparatively short-time uctuations of energy represented by the overlap 13. Thus the automatic volume control prevents the amplitude of the output-pulses from lampliiier 5 from varying with distance of the target from the transmitter or from the receiver antenna 3. Interference beating between the direct and reflected radio waves at the receiver may be rendered unimportant by making the pulse repetition rate at least several times this beat frequency.

It will be noted that Ia circuit may be embodied in the amplifier 6 which will cause the output current of the latter to vary only in response to an overlap 13 of a given width. For example, the output circuit of the amplifier 6 may be constructed to iluctuate only in response to the pulse width represented by the overlap 13 in FIG. 2e.

Under such conditions there would be no energization of the trigger tube 7 while the moving body was separated from the tanget by the 3000 feet represented in FIG. 2a because there would be no overlap between the pulses. Similar statements apply to the 2000 feet distance and the 500 feet distance covered, respectively, by FIGS. 2b and 2e. While there would be an overlap in `the 375 feet distance represented by FIG. 2d, the overlap would be too short to cause iluctuation of the output current of amplifier 6 inasmuch kas the latter is arranged to uctuate only in response to an overlap of the length of 13 in FIG. 2e.

When, however, the moving body had reached the 250 feet distance represented by FIG. 2e, the overlap of the right duration would be present on the input circuit to amplifier 6; trigger tube 7 would Ibe energized and the actuated device 8, for example, the bomb detonator, would be actuated.

It will be noted from the observation of FIGS. 2d, 2e, 2f and 2g that the time interval separating the front (i.e. left-hand) edge of pulse 11 from the front edge of overlap 13 is proportional to the distance separating the moving body from the target. If now the duration of the pulse 11 is increased (i.e. pulses 11 and 12 become wider in FIG. 2), but the amplifier 6 remains unaltered so that it produces a current pulse in its output circuit only in response to overlap of the width shown in FIG. 2e, the distance between the body and the target at which the trigger tube 7 will be energized will still be proportional to the time separating the front edge of pulse 11 from the front edge of pulse 13. From this it follows that the distance separating the body from the target at which trigger tube 7 is energized can be varied at will by varying the duration of the pulses from transmitter 1. In'partic- 4 ular by reducing the length of the transmitted pulses 11 to equality with the critical value of the overlap pulse 13 at which the amplifier 6 produces a current fluctuation in its output circuit, the distance separating the moving `body from the target when the trigger 7 is actua-ted can 'be reduced to zero.

The foregoing relationships between pulse width and distance from the target `at which the overlap 13 attains the predetermined critical value are illustrated in FIGS. 3a to 3d inclusive. These figures cover operation with the trigger tube 7 becoming energized by an overlap 13 of onehalf a microsecond. FIG. 3a shows a transmitter pulse duration of 2.5 microseconds and represents conditions at which the pulse 11 and the pulse 13 would have an overlap just suiiicient to energize trigger tube 7, i.e. an overlap equal to one-half a microsecond. The distance separating the body from the target under the conditions represented by FIG. 3a would be approximately 1000 feet. Hence, at l000 feet separating the body from the target, the actuated device 8 would be operated by transmitting from the transmitter 1 a pulse having a width of 2.5 microseconds.

If now the transmitted pulse duration is decreased to one and one-half microseconds, the conditions in antenna 3, when the overlap is one-half a microsecond, are represented by FIG. 3b. Since the trigger tube is actuated when such a one-half microsecond overlap occurs and the distance separating the moving body from the target at which the pulses 11 and 12 overlap by a one-half microsecond is 500 feet, it is obvious that the actuated device 8 will be operated at 500 feet distance by reducing the intermediate pulse with to one and one-half microseconds.

iFIG. 3c corresponds to a pulse width of one microsecond with a one-half microsecond overlap, and represents conditions occurring when the separation between the target and the moving body is 250 feet.

FIG. 3d represents conditions existing at the receiver when the transmitter pulse is reduced to one-half a microsecond and is correspondingly equal to the critical overlap. Such overlap occurs when the distance separating the target from the moving body is zero.

Turning now to FIG. 4, the latter represents one form of receiver circuit which I believed to be well adapted to carry out the principles of my invention, as above outlined. A receiving antenna 21, 22, which may be a dipole or other type suited to the wave length employed, is carried by the bomb or other moving body and energizes an inductive winding 23 having the similar electrodes of a pair of rectifiers 24, 25 connected to its opposite ends. The remaining terminals of the rectiers 24, 25 are respectively connected to one terminal of a capacitor 26 having its other terminal connected to the midpoint of the winding 23. It will be seen that the winding 23 and rectiiiers 24 and 2S will charge the capacitor 26 to a potential proportional to the amplitude of the radio waves incident upon the antenna 21, 22. The terminals of capacitor 26 are bridged by three serially connected resistors 27, 28 and 29, which are of suitable value so that the members 23, 24, 25, 26, 27, 28 and 29 constitute a detector producing current pulses in resistor 27 corresponding in wave form to the envelope of the above mentioned pulses of radio waves. One terminal of the resistor 27 is connected through a capacitor 31 to the control electrode of a suitable electron discharge amplifier tube 32, the cathode of which is connected to the other terminal of the resistor 27. The cathode `of the tube 32 is likewise connected through a condenser 33 to theterminal of the resistor 28 which is remote from resistor 27, and a resistor 35 connects the control electrode of tube 32 to that same terminal. A capacitor 36 shunts the terminals of the resistor 29, and a resistor 37 connects the midtap of the winding 23 with the anode circuit of the tube 32.

The anode of the tube 32 is connected through the primary winding 38 of a transformerA and a resistor 39 to the positive terminal of a direct current source having its negative terminal connected via ground to the common terminals of resistors 28 and 29.

The connections of the tube 32 thus described constitute it a combined ampli-lier and automatic volume control device for signals incident upon the antenna 21, 22. An automatic control voltage is developed across the resistor 2S and; capacitor 33 and is impressed both upon the tube 32 and upon the detector comprising rectifers 24, 25 and capacitor 26. The resistors 29 and 37 are so proportioned as to produce a potential drop in resistor 29 equal and opposite to that produced in resistor 28 when no signal is impressed ,on the control circuit of tube 32. As a result. of this arrangement, the detectorcomprising rectiers 24, 25 and capacitor 26 remains unbiased when no signal is being received by the antenna 21, 22. The output voltage of the detector appears across the resistor 27 and is impressed thereby on the tube 32.

Associated with the winding 38 to constitute an efficient pulse transformer are a pair of windings 41, 42. The winding 41 has one terminal connected to the control electrode of an electron discharge tube 43 of a type suitable to amplify high frequencyY pulses and having its anode connected to lreceive current through the above mentioned resistor 39. The cathode of the tube 43 is connected through a resistor 44 in series with a second resistor 45 to the negative terminal of a suitable direct current voltage vsource having its positive terminal grounded. The other yterminal of the winding `41 is connected through a resistor 46 to the negative terminal of another direct current voltage source having its positive terminal connected to ground.

One terminal of the Winding 42 is connected to the common terminal of resistors 44 and 45 and also through a pulse by-pass capacitor 47 to the last mentioned terminal of the winding 41. The other terminal of winding 42 is connected through a distributed inductance 48 to the cathode of the tube 43. The distributed inductance 48 is associated with a similarly distributed capacitance 49 which is connected to the common terminal of the resistors 44 and 45.

The elements 48, 49 constitute 'a well known type of time delay circuit which produces a voltage at its output terminal of substantially similar wave \form to that impressed on its input terminal lbut delayed by a predetermined time interval With reference thereto.

` The common terminal of the resistors 44 and 45 is connected to the control electrode of a gaseous electric discharge tube 51 having its 'anode connected to receive current through the resistor 39 or alternatively to the positive terminal of another direct current voltage source having its negative terminal grounded. Tube 151 has its cathode grounded. A capacitor `52 connected in series with an actuated device or work rcircuit 53, which may, for example, be the control of a bomb detonator, is bridged between the anode and cathode of the tube 51. A pulse by-pass capacitor 54 grounds the negative terminal of the resistor 45. y

The elements 21 through 42 -above mentioned correspond to the antenna 3 and detector 4 in FIG. l; the elements 43 through 49 in FIG. 4 correspond to the amplier and pulse width discriminator 6 of FIG. 1; the tube 51 corresponds to the trigger tube 7 of FIG. 1; and the detonator 53 corresponds to the actuated device 8 of PIG. 1. Y

The resistor 28 and the remaining elements energizing tube 32 are initially given such values that in the absence of energy `incident upon the antenna 21, 23, the tube 32 is biased nearly to cut off; and the values of 4the potential impressed through resistor 46 on tube 43 and through resistor 45 on tube 51 are made such that tubes 43 and '51 are biased below cutofr.

The operation of the arrangement just described is believed to 'be as follows. When a wave pulse is incident upon the antenna 21, 22 rfrom transmitter 1 Ia voltage pulse corresponding in form to the envelope of said incident pulse is impressed by winding 41 upon tube 43. However, the volume control -for the detector 24, 25 and amplifier 32 is s o adjusted that the pulse impressed on tube 43 by winding 41 is insuicient-to overcome the negative bias impressed through resistor 46 to a suicient degree to render the tube 43 conductive.

The above mentioned incidence of a pulse on antenna '21, 22 lwill likewise impress -a voltage across the resistor 44 in the cathode circuit of tube 43, but this pulse will be delayed relative to the pulseim-pressed on tube 44 by winding 41 in virtue of the action of the time delay device 48, 49; hence, the voltage pulses respectively impressed on the control electrodey of tube 43 will not-occur simultaneously and neither alone will suice to'render trigger tube 43 conductive.

It will however be evident that the retiection from the target of the above-mentioned pulse emitted from transmitter 1 will cause tube 32 to impressa pair of successive voltage pulses through windings 42 and 41 on tube 43; but this freected pulse Will follow the directly-incident pulse 'already mentioned by a time interval sutcient for radio waves to travel from antenna 3 to the targetand back. The adjustment of the amplier 32 will again be such that this pulse will of itself be insufficient to cause tube 43 to conduct current. Each of these time-separated pulses corresponds to pulse 12 in FIG. .2a.

When the timing of pulses 11 and 12 is right the pulses 11 and 12 overlap to form Ian overlap pulse 13 equal to their surn in amplitude; but tube 43 is so adjusted that even the overlap pulse 13 impressed by Winding 41 alone, or by winding 42 alone, does not suffice to make tube 43 conduct. It will be evident that unless the pulse 13 has a duration equal to the time delay interposed by the time delay elements 48, 49, the voltage pulses impressed respectively by the windings 41 and 42 on the tube 43 can never overlap, and yaccordingly tube 43 will not be rendered conductive when the overlap 13 has a value less than the critical value set by time delay network 48, 49. However, once the overlap 13 exceeds in duration the time-delay due to network 48, 49, the voltage pulse impressed -by windings 41 and 42 overlap in time and add their, eiects thereby rendering tube 43 conductive. Fluctuatious in the output current of tube 43 llow through .the resistor 45 `and capacitor 54 and thereby impress a positive pulse on the control electrode of trigger tube 51 causing the latter to become conductive. The sudden pulse of current in the output circuit of tube 51 energizes det-onator 53 through the capacitor I52 to operate the control device.

While I have described specic types of automatic volume control for the detector 24, 25, 26 and amplifier 32, and have described a specific type of time delay network 48, 49 for rendering the ampliier 43 responsive only to :pulses of a predetermined duration, there are rother types of yautomatic volume control circuits `and time delay networks known to those skilled in the art which may be substituted `for the elements I have described in detail in ways evident to those skilled in the art.

I claim las my invention:

l. In combination with a transmitter of pulsed radiant energy, a rst body adapted to reect saidl energy, a second body movable relative to said rst body, means on said second body for receiving radiant energy both from said transmitter Iand from said irst body, a circuit which is responsive to the output of said means for receiving, and means -for rendering said circuit unresponsive where there is overlap of less than a predetermined duration in pulses received from said transmitter and said rst body but responsive when said overlap is greater than said duration.

2. An arrangement as s-pecied in claim 1 in which said second body carries an explosive which has a detonator controlled by said circuit.

'3. In combination with a transmitter off pulsed radiant energy, a first body adapted to reflect said energy, a second body movable relative to said first body, means ou said second body 'for receiving radiant energyboth from said transmitter and from said first body, a circuit which is responsive to the output of-said means for receiving, and means for rendering said circuit unresponsive where there is overlap of less than a predetermined duration in pulses received from `said transmitter land said rst body but responsive when said overlap is greater than said duration, said transmitter beingprovided with means for varying the duration of said pulses, in accordance with the will of the operator.

4. An arrangement as specified in claim 3 in which said second body carries an. explosive-which has a detonator controlled by said circuit.

5. In combination with a transmitter of pulsed radiant energy mounted on a first body, ya target, 'and a second body movable relative to said target and to said tirst body, means on said second body for receiving radiant energy directed from said transmitter and reflected from said target, a detector which is responsive to the output of said means for receiving and provided with `an automatic volume control circuit, amplication means connected to receive the output of said detector, and means for preventing variations in the output current of said amplication means` except when direct and reected radiant energy originating at said transmitter 'are incident upon said receiving means during an overlap of predetermined duration.

6. In combination a. transmitter of pulsed radiant energy mounted on a iirst body, a target, and a second body movable relative to said target and to said rst body, means on said second body for receiving radiant energy directed from said transmitter and reflected from said target, a detector which is responsive to the output of said means for receiving and provided with lan automatic volume control circuit, amplification means connected to receive the output of said detector, and means for preventing variations in the output current of said amplification means except when direct and reilected radiant energy originating at said transmitter are incident upon receiving means during an overlap of predetermined duration, said transmitter being provided with means for varying the duration of its output pulses.

References Cited in the le of this patent UNITED STATES PATENTS 2,134,716 Gunn Nov. 1, 1938 2,176,469 Moueix Oct. 17, 1939 2,382,058 Hull Aug. 14, 1945 2,403,527 Hehshberger July 9, 1946 2,404,527 Potapenko July 23, 1946 2,410,424 Brown Nov. 5, 1946 2,412,632 Sanders et al Dec. 17, 1946 2,415,855 Skellett Feb. 18, 1947 2,416,088 Deerhake Feb. 18, 1947 

